The invention relates to an aid for assisting the driver of a motor vehicle, particularly when driving a vehicle in reverse gear.
When driving a vehicle in reverse gear it may be difficult to see into the space immediately behind the rear of the vehicle. For example, because of steep bodylines on some vehicles it is difficult to detect the end of the vehicle. This is also the case with closed delivery vans or trucks with closed superstructures.
When driving a vehicle in reverse a driver may not be able to detect an obstacle in the path of the vehicle.
For this purpose, aids are known which permit obstacles in the zone behind a reversing motor vehicle to be detected, and corresponding signals to be output to the vehicle driver.
Utility Model DE 87 17 494 U1 describes a parking aid. Arranged on the rear side of a motor vehicle are a transmitter, which emits an infrared beam or laser beam, and a receiver, which receives the measuring beam reflected by an object. The measured distance from the object is displayed to the driver by means of an LED display chain via an electronic evaluation system.
It is certainly possible with this parking aid to determine the distance between the transmitter/receiver and the detected object. However, the driver may still be unable to gain a complete picture of the actual path of the vehicle and of any objects located therein. Because of a lack of sufficient information, the driver may execute a driving manoeuvre which causes an undetected object to be driven into. Thus, in particular, the rear corner regions are particularly of interest when the vehicle is at an oblique angle to the detected object, but a simple distance measurement determines only distance from the middle of the rear end.
DE 43 03 066 C2 describes a further parking aid. In order to facilitate parking, in particular of large vehicles, a distance-warning device with an optical sensor system is provided in this case. The sensor system is intended to detect an obstacle in the form of an object or a vehicle part while taking account of a minimum distance. The radiation transmitter and radiation receiver used are aligned obliquely downwards, the radiation lobes, which are correspondingly directed obliquely downwards, marking the range of the minimum distance. A range measurement is carried out when an obstacle penetrates the radiation lobe. The pulsed radiation components reflected at the object are detected by the respective radiation transmitter and fed to corresponding signal conditioning and signal processing.
A simple distance measurement is also carried out in the case of this parking aid. The driver is warned when he drives up too close to a detected object, but, once again, cannot gain a picture of the rear danger zone.
The known aids have in common the disadvantage that a plurality of obstacles, which are in different positions and/or of different height, in the rear danger zone cannot be detected with adequate reliability when the relevant object is not completely detected by the static measuring beams. With the aid of the known parking aids, the driver is not able to establish where the vehicle rear end is located relative to the objects located in the rear danger zone. Given this knowledge the driver would be able to decide on a specific steering movement and/or a specific driving direction in order to drive around the object determined and/or to avoid a collision with it.
The object of the invention is to specify a reversing aid which, in particular in the case of reversing, supplies the driver with reliable information on the respective spatial arrangement of objects located in the rear danger zone relative to the vehicle. Moreover, the reversing aid according to the invention is intended to make it possible to implement the detection of objects and processing of information in a way which is particularly simple, robust, reliable and cost-effective.
This object is achieved according to the invention by means of a reversing aid having the features of the claims. The subclaims advantageously relate to developments of the reversing aid according to the invention.
In the case of the reversing aid according to the invention, there are arranged at the rear end region of the motor vehicle at least one transmitter for emitting measuring beams into the rear danger zone, and at least one receiver for receiving beams reflected at at least one detected object. A distance-measuring device determines the distance between the vehicle and the detected object, which is represented optically with the aid of a display device.
In accordance with a basic idea of the invention, the reversing aid has a measuring beam horizontal guidance system for the purpose of periodically scanning a predetermined angle range in the horizontal plane. In this case, an evaluation device determines the position of the detected object in the horizontal plane relative to the vehicle rear end, and the extent of the width, or the width of the xe2x80x9cfront edgexe2x80x9d of the detected object. The position and the extent of the width of the detected object in the horizontal plane relative to the vehicle rear end are represented on a display screen.
Since a real pictorial representation of the rear danger zone is dispensed with, imaging optical systems can be greatly simplified, and therefore produced cost-effectively. Errors can be calibrated out in a simple way.
The reversing aid can also be used, in a modified fashion, to look ahead, for example in order to display for trucks the adequate clearance of tunnels or passages.
In accordance with a further basic idea of the invention, the measuring beam horizontal guidance system cooperates with a measuring beam vertical guidance system. A predetermined solid angle range can be periodically scanned in the horizontal and vertical directions in the manner of a scanning or rasterizing operation owing to the fan-shaped design, resulting therefrom, of a band of light together with the horizontal movement thereof. For this purpose, the evaluation device comprises a height-determining device for the purpose of determining the extent of the height of the detected object, which can be represented pictorially with the aid of representational means of the display screen.
The driver can use the representation of the rear zone with relative positions and widths of the detected objects in conjunction with data on their height and on the basis of his own intelligence to undertake a realistic assessment of the zone behind the vehicle. When reversing, he can follow the movement of his own vehicle and/or its rear end with the aid of the pictorial representation.
In order to be able to make a sufficiently accurate statement on the height of the detected objects, and to minimize the technical outlay, the solid angle range scanned by the measuring beam vertical guidance system can be subdivided into a plurality of height angle ranges. In this case, each detected object point situated in a specific height angle range is assigned a height range value. In order to distinguish between objects of different height, and to undertake assignment relative to specific object heights, the representational means of the display screen can have for each of the height range values a different coloured, hatched and/or similar distinguishable representational form.
The distance of the detected object can be calculated by evaluating the geometrical desired values. However, in the case of such a calculation no account is taken of any distortions or similar disturbances. It is therefore provided according to the invention to determine the distance and/or the position and the extent of the width of the detected object with the aid of look-up tables with predetermined desired values from the prescribed optical and geometrical factors of the receiver. The disturbing factors can be taken into account in the look-up tables. No use is made of appreciable computer power, nor is there, therefore, any need for software. In the case of very large piece numbers, it is expedient to integrate the entire electronic evaluation system into one to two chips.
In order to be as secure as possible against unwanted light, the transmitter can have at least one narrow-band or monochromatic light source. Likewise, the receiving cameras are to be of narrow-band design and to be sensitive only in the wavelength region used by the transmitter.
The measuring beam horizontal guidance system and/or the measuring beam vertical guidance system can have a mirror wheel and/or LCD stops and/or similar aids for measuring-beam scanning. The measuring-light beam can easily be caused to sweep over the desired solid angle range with the aid of these measures. The use of different imaging sensors, for example for ultrasound or radar, is conceivable.
The receiver can have at least one imaging optical system with a plurality of light-sensitive semiconductor sensors arranged in the image plane thereof. The semiconductor sensors are inexpensive and sensitive to the wavelength used.
It is possible to arrange in the image plane of the receiver a number of sensor rows which corresponds at least to the number of height angle ranges into which the scanned solid angle range is split up. By suitably limiting the number of rows, it is possible to realize a receiver of small design in conjunction with satisfactory height resolution.
The optical transmitter and camera(s) can be produced and calibrated as a finally assembled unit.
Further advantages, features and details of the invention will become clear with the aid of the following description in conjunction with the attached drawings, in which: